1. Field of the Invention
The present invention relates to the conversion of raster data to vector data and, more particularly, the present invention relates to the conversion of oscilloscope raster display data into vector data for driving a vector output device such as a plotter.
2. Statement of the Problem
Raster displays are commonly used for video monitors. The storage of raster display information is done in a cartesian coordinate (X,Y) two dimensional memory array referred to generally as a memory plane or bit map. Each pixel in the display monitor is represented by a bit of information in the memory plane. If the bit in the memory plane is a 1, then the corresponding pixel in the display monitor is fully illuminated. If the bit in the memory plane is a 0, then the corresponding pixel in the display monitor is not illuminated. A hard copy of the raster display occurring in a monitor can be obtained from a raster printer. Again, each bit in the memory plane provides a corresponding "dot" or "no dot" in the raster printer.
It is desirable to use a vector plotter to provide hard copies of the raster display in the monitor. For example, oscilloscopes generally have raster displays upon which the waveforms being measured are viewed. It is desirable to functionally interconnect such oscilloscopes with vector plotters. However, fundamental differences exist between raster and vector data representations. A vector (or line) is represented by vector beginning and end points. Each vector beginning and end point corresponds to an X,Y coordinate in the cartesian coordinate system. The vector is then represented by the two points and the plotter draws a line from the beginning point to the end point. Due to such fundamental differences between raster and vector data representation, it is difficult to reproduce an accurate representation of a raster display on a vector device such as a plotter.
In FIG. 1, one prior solution to the problem of converting raster data to vector output is illustrated. Base data 100 is created, such as by an oscilloscope generating sampled waveforms from a device or system under test. The generation of base data 100 is well known in the art. The base data 100 is accessed by a set of raster draw routines 110 which delivers the raster data to a raster memory plane 120. The raster draw routines 110 provide the necessary indicators, the necessary configurations and statuses, the markers, the graticules, and of course the waveforms being sampled into the raster memory plane 120 for display in a raster display 130. The binary bit appearing in the raster memory plane 120, as discussed above, has a corresponding pixel in the raster display 130. When it is desired to connect a vector plotter 140, a separate set of vector draw routines 150 must be created in software to provide the indicators, configurations and statuses, markers, graticules and the sampled waveforms. The provision of separate vector draw routines 150 is expensive in that it requires an initial overhead at a product's inception to create the separate set of routines 150. When vector draw routines are specifically created for one product, they do not have portability among other products using raster displays. Additionally, once the product is introduced and supported to the customer base, the addition of new markers and indicators in the display requires the creation of new corresponding software to the vector draw routines 150. Hence, such routines 150 must be continually supported. Finally, such vector draw routines do not accurately reproduce the pattern on the display.
A need therefore exists for providing raster to vector conversion without requiring the creation of separate vector draw routines 150. Such a solution should not require additional overhead at the inception of each different product nor should it require downstream support. The conversion should be completely portable from product to product and, yet, should provide high quality conversion so that the vector output corresponds one for one with the raster display.